本研究目的為在鎂釔鋅合金表面，進行微弧氧化表面處理技術鍍上氧化鋯陶
瓷膜，試圖強化鎂釔鋅合金的各項表面性質，使鎂合金能早日應用於各項工業技
術上。而部分文獻中提到定電流模式時，正負電流比小於1 的情況下，微弧放電
反應將會有一個明顯由強轉弱的弱工作區現象(Soft regime)，而弱工作區現象將
使反應中破壞的現象減輕，且有修復表面膜層的機制，且此現象會因為微弧氧化
的各項參數影響，本論文也會在實驗過程中，對弱工作區現象的發生及成膜機制
做一個研究及探討。
首先為了找出有利於鎂合金鍍膜的參數，本實驗先以市面上常見的 AZ91D
鎂合金為基材進行微弧氧化鍍膜。之後更改電解液參數得到了製程穩定化的效果，
鍍膜反應順利進行。製程穩定化之後，將奈米氧化鋯顆粒添加於電解液中進行實
驗，發現添加奈米氧化鋯後膜層孔洞中會有明顯的白色區塊填補作用，但是會導
致弱工作區電壓趨勢不一定會隨反應變弱而下降。而成膜機制方面在實驗中觀察
到沒有添加奈米顆粒的膜層在弱工作區之後會開始生長緻密氧化鎂層使表面孔
洞底部與基材表層被緻密層隔開而產生一個類似填補的現象。添加奈米顆粒後會
發現顆粒會填入孔洞中達到更進一步的填補。.
之後為了降低奈米氧化鋯顆粒帶來的不穩定性，因此第一部份實驗將會找出
可用於在鎂釔鋅合金表面進行微弧氧化鍍膜的電解液參數，本部份會調配氟鋯酸
鉀/氫氧化鈉莫耳比1/4 且於每升水溶液含 5 克的六偏磷酸鈉及每升20 毫升的
奈米氧化鋯顆粒中改變氟鋯酸鉀/氫氧化鈉重量比為6: 3.4, 7.5: 4.25 and 9: 5.1 的
3 組電解液參數，發現提高鋯酸鹽類濃度可以解決奈米顆粒帶來製程不穩定性的
問題，同時也觀察到隨著鋯酸鹽類濃度提升，弱工作區會發生得越早，將使反應
由強轉弱的現象越早發生。硬度方面看到表面硬度有明顯改善，但是與以前研究
成果相比是偏低的，此現象可能是因為陽極工作周期較短(10%)造成鍍膜時間不
夠，使表面機械性質提升的效果有限。腐蝕阻抗方面看到第1 組與第3 組溶液的
ii
鍍膜在52.5 分鐘後都有一個阻抗下降的趨勢，這可能與材料熱膨脹係數的差異，
與溶液導電度過高造成膜層所受熱應力過大使膜層被嚴重破壞所致，而第2 組電
解液發現其腐蝕阻抗值隨著工作時間穩定增加，且電壓趨勢也相對穩定，因此
認為較適合在鎂釔鋅合金鍍膜的電解液參數在第2 組電解液參數附近。而在本實
驗的電解液鍍膜的相結構分析發現鍍膜時間60 分鐘前後將有一個原本以
Rhombohedral 相氧化鋯為主的膜層將會被Cubic 相氧化鋯取代現象，其原因可歸
諸於氧化鎂與氧化鋯的反應。

The purpose of this study is to coating zirconia oxide layer on Mg-Y-Zn alloy using
Plasma Electrolytic Oxidation (PEO) to strengthen surface and corrosion-resistance
properties. In some previous studies, when the positive and negative current ratio is
less than 1 in the constant current mode, the microarc discharge reaction may switch
from “arc” to “soft” regime. In the soft regime, the reaction may reduce damage and
the cracks of the oxide layer will be fixed, and this phenomenon may be affected by
the parameters of Plasma Electrolytic Oxidation. In this thesis, we will also study the
occurrence and mechanism of soft regime in this experiment.
Firstly, in order to find the suitable parameters to coat oxide layers on Mg alloy, we
use AZ91D for the micro-arc oxidation coating, and change the electrolyte parameters
to achieve process stabilization and smooth coating reaction. After the process was
stabilized, the nano-zirconia particles were added to the electrolytes for experiment. It
was found that there was a significant pore-filling effect in the coating surface after
adding nano zirconia, but the trend of voltage decline at the soft regime was not
observed all the time and voltage instability was seen. We also found that without
nano-particle addition the PEO process grow denses MgO oxide layer at the interface
region of the Mg alloy substrate so that the deposited bottom layer with defects and
pores close to the substrate interface is separated by the MgO dense layer. On the
other hand, after adding the ZrO2 nanoparticles, the particles will be filled into the
pores at the interfacial region to achieve denser coating.
In order to reduce the instability caused by the addition of nano-zirconia particles,
the first part of the experiment demonstrates that the electrolyte and the working
parameters can be used for plasma electrolytic oxidation coating on the surface of
Mg-Y-Zn alloy. At the second part, we prepare three groups of electrolytes with a
iv
constant K2ZrF6 / NaOH molar ratio of 1/4 and change the weight ratios of 6: 3.4, 7.5:
4.25 and 9: 5.1 in 2 liter solution of 5 g/l (NaPO3)6 and 20 ml/l nano ZrO2 particles
and demonstrated appropriate zirconate concentration and PH value of the electrolyte
can solve the problem of nano-particles process instability. With increasing zirconate
concentration, the soft regime would occur quickly, and switch the reaction from
strong to weak earlier. Surface hardness of the coatings were improved, but if
compared with the previous research results, they are lower, probably attributed to the
short duty cycle (10%) induced low plasma. If the coating time is not enough or
plasma is weak, the surface mechanical properties contributed by the coating layer
may be limited. Corrosion resistance tests show that the first group and the third
group of the solution after 52.5 minutes PEO treatment exhibit a downward trend in
corrosion resistance, which may be attributed to the difference of the thermal
expansion coefficients of phases between the substrate and coatings, causing
detrimental thermal stress on the oxide layer. The corrosion resistance of the second
group of electrolytes (K2ZrF6 / NaOH weight ratio of 7.5: 4.25) was found to exhibit
higher corrosion resistance value with the working time and larger workable time
region, and the voltage trend was relatively stable. Therefore, it was considered that
the suitable electrolyte parameters of the coating on the Mg-Y-Zn alloy. Using the
current electrolytes, phase structure analysis of the coating showed that the coating
time before and after 60 minutes exhibit a Rhombohedral/Cubic phase change
phenomenon of the zirconia-based film, implying the phase transition due to the
reaction of MgO and ZrO2 phases.

[1] Michael M. Avedesian and Hugh Baker, "Magnesium and Magnesium alloys, ASM Specialty Handbook.", 1999.
[2] Yoshihito Kawamura, Kentaro Hayashi, Akihisa Inoue, Tsuyoshi Masumoto "Rapidly Solidified Powder Metallurgy Mg97Zn1Y2Alloys with Excellent Tensile Yield Strength above 600 MPa" Materials Transactions, Vol.42, No.7 (2001) pp.1172 to 1176
[3] J.F. Fan, Ch.L. Yang, G. Han, S. Fang, W.D. Yang, B.S. Xu "Oxidation behavior of ignition-proof magnesium alloys with rare earth addition", Journal of Alloys and Compounds Volume 509, Issue 5, 3 February 2011, Pages 2137–2142
[4] G. Garces, P.Perez, S.Cabeza, H.K.Lin, S.Kim, W.Gan, P.Adeva "Reverse tension/compression asymmetry of a Mg–Y–Zn alloys containing LPSO phases" Materials Science & Engineering A 647 (2015) 287–293.
[5] G. Song, A. Atrens, “Understanding magnesium corrosion – a framework for improved alloy performance.” Adv Eng Mater, 5, pp. 837-858,2003
[6] M. Pourbaix, "Atlas of Electrochemical Equilibtia in Aqueous Solution." NACE, Houston, TX, USA, 1974.
[7] R.Ambat, N.N. Aung and W.Zhou, "Studies on the influence of chloride ion and pH on the corrosion and electrochemical behavior of AZ91D magneium alloy", Journal of Applied Electrochemistry, vol.30, p.865, 2000.
[8] R. Ambat, Naing Naing Aung and W.zhou, "Evaluation of microstructural effects on corrosion behavior of AZ91D magnesium alloy", Corrosion Science, Vol.42, p.1433, 2000.
[9] W.M. Chan, F.T. Cheng, L.K. Leung, R.J. Horylev and T.M. Yue, "Corrosion behavior of magnesium alloy AZ91 and its MMC in NaCl solution", Corrosion Reviews, Vol.16, p.43, 1998.
[10] N.P. Sluginov, "Electric discharges in water", J. Russ. Phys. Chem. Soc.,12 1-2 Phys. (1880) 193.
[11] G.A. Markov, G.V. Markov, "The formation method of anodic electrolytic condensation", 1976.
[12] P. Kurze, W. Krysmann, G. Marx, "Anodic Oxidation of Aluminum by a Spark Discharge in Aqueous Electrolytes", Wiss. Z. T. Hochesh. Karl-Marx-Stadt, 1982, 24.6: 665-671.
[13] A.L. Yerokhin, X. Nie, A. Leyland, A. Mattews and S.J. Dowey, "Plasma electrolysis for surface engineering", Surface and Coatings Technology, 122 73-93, 1999.
[14] R.O. Hussein, X. Nie, D.O. Northwood, "An investigation of ceramic coating growth mechanisms in plasma electrolytic oxidation (PEO) processing", Electrochemical Acia 112 (2013) 111-119.
[15] Hyun Sam Ryu, Seong-Hyeon Hong, "Effects of KF, NaOH and KOH Electrolytes on Properties of Microarc-Oxidized Coatings on AZ91D Magnesium Alloy", Thin Solid Films 494 (2006) 296-301.
[16] Y. Ma, X. Nie, D.O. Northwood, H. Hu, "Systematic study of the electrolytic plasma oxidation process on a Mg alloy for corrosion protection", J. Am. Ceram. Soc., 91(2) 555-558 (2008).
[17] Z.P. Yao, H.H. Gao, Z.H. Jiang, "Structure and Properties of ZrO2 Ceramic Coatings on AZ91D Mg Alloy by Plasma Electrolytic Oxidation", J.Am. Ceram. Soc., 91(2) 555-558(2008).
[18] Mu Weiyi, Han Yong, "Study on Micro-Arc Oxidied Coatings on Magnesium in Three Different Electrolytes", Rare Metal Materials and Engineering, 2010, 39(7): 1129-1134.
[19] D. Sreekanth, N. Rameshbabu, K. Venkateswarlu, "Effect of various additives on morphology and corrosion behavior of ceramic coatings developed on AZ31 magnesium alloy by plasma electrolytic oxidation", Ceramics International 38(2012) 4607-4615.
[20] Shuyan Wang, Yongping Xia, Li Liu, Naichao Si, "Preparation and performance of MAO coatings obtained on AZ91D Mg alloy under unipolar and bipolar modes in a novel dual electrolyte", Ceramics International 40 (2014) 93-99.
[21] Guo-Hua Lva, Huan Chena, Wei-Chao Gua, Li Lia, Er-Wu Niua, Xian-Hui Zhangb, Si-Ze Yanga, “Effects of current frequency on the structural characteristics and corrosion property of ceramic coatings formed on magnesium alloy by PEO technology”, Journal of materials processing technology 208 (2008) 9-13.
[22] P. Bala Srinivasan, J.Liang, C.Blawert, M. stormer, W. Dietzel, "Effect of current density on the microstructure and corrosion behavior of plasma electrolytic oxidation treated AM50 magnesium alloy", Applied Surface Science 255 (2009) 4212-4218.
[23] Kai Wang, Bon-Heun Koo, Chan-Gyu Lee, Young-Joo Kim, Sung-Hun Lee, Eungsun Byon, "Effects of electrolytes variation on formation of oxide layers of 6061 Al alloys by plasma electrolytic oxidation", Trans. Nonferrous Met. Soc. China 19, 866-870, 2009.
[24] J. Martin, A. Melhem, I. Shchedrina, T. Duchanoy, A. Nominé, G. Henrion, T. Czerwiec, T. Belmonte, “Effects of electrical parameters on plasma electrolytic oxidation of aluminium”, Surface & Coatings Technology 221 (2013) 70–76
[25] F. Jaspard-Mécuson, T. Czerwiec, G. Henrion, T. Belmonte, L. Dujardin, A. Viola, J. Beauvir, “Tailored aluminium oxide layers by bipolar current adjustment in the Plasma Electrolytic Oxidation (PEO) process“ Surf. Coat. Technol. 201 (2007) 8677–8682
[26] LIU Feng, SHAN Da-Yong, SONG Ting-Wei, HAN En-hou, "Formation process of composite plasma electrolytic oxidation coating containing zirconium oxides on AM50 magnesium alloy", Tran. Nonferrous Met. Soc. China 21 (2011) 943-948.
[27] Yanhong Gu, Sukumar Bandopadhyay, Cheng-fu Chen, Yuanjun Guo, Chengyun Ning, "Effect of oxidation time on the corrosion behavior of micro-arc oxidation produced AZ31 magnesium alloys in simulated body fluid", Journal of Alloys and Compounds 543 (2012) 109-117.
[26] M.K. Reser, "Phase Diagram for Ceramics", Am. Ceram. Soc., Columbus, Ohio (1975).
[28] R.C. Garive, "Zirconia Dioxide and Some of Its Binary System", in High Temperature Oxides, Vol.5, Ed. By A.M. Alper, Academic Press, New York, (1970), Chap.4.
[29] R.C. Garive, "The Occurrence of Metastable Tetragonal Zirconia As a Crystallite Size Effect", J. Phys. Chem, 69[4] 1283-43 (1965).
[30] R.H. J.Hannink, "Magnesia-Partially Stabilized Zirconia: The Influence of Heat Treatment on Thermomechanical Properites", J. Aust. Ceram. Soc., 18[2] 53-62 (1982).
[31] S.C. Farmer and L.H. Schoenlein, "Precipitation of Mg2Zr5O12 in MgO-Partially Stabilized ZrO2", J.Am. Ceram. Soc., 66, 104-9 (1987).
[32] R.H.J. Hannink, "Microstructural Development of Sub-Eutectoid Aged MgO-ZrO2 Alloys" J.Mater. Sci., 18, 457-470 (1983)
[33] R. Chaim and D.G. Brandon, "Microstructure Evolution and Ordering in Commercial Mg-PSZ", J. Mater. Sci., 19, 2934-2942 (1984).
[34] S. C. Farmer and L. H. Schoenlein, “Precipitation of Mg2Zr5O12 in MgO-Partially-Stabilized ZrO2.”, J. Am. Ceram. Soc., 66, 107-9(1987).
[35] Zeeshan Ur Rehman, Seong Hun Shin, Imad Hussain, Bon Heun Koo, "Structure and corrosion properties of the two-step PEO coatings formed on AZ91D Mg alloy in K2ZrF6-based electrolyte solution" Surface & coatings Technology 307 (2016) 484-490.
[36] Haihe Luo, Qizhou Cai, Bokang Wei, Bo Yu, Dingjun Li, Jian He, Ze Liu, "Effect of (NaPO3)6 concentrations on corrosion resistance of plasma electrolytic oxidation coatings formed on AZ91D magnesium alloy" Journal of Alloys and Compounds 464 (2008) 537-543
[37] Alexandre Nominé, Julien Martin, Cédric Noël, Gérard Henrion, Thierry Belmonte, Ilya V. Bardin, Petr Lukeš, “Surface charge at the oxide/electrolyte interface: Toward optimization of electrolyte composition for treatment of Aluminum and Magnesium by Plasma Electrolytic Oxidation”, Institute of Plasma Physics, Academy of Sciences of the Czech Republic, v.v.i. Za Slovankou 3, Prague 182 00, Czech Republic
[38] 陳永祿, 周振嘉, “以微弧氧化法於AZ91D鎂合金上鍍製矽酸鹽及鋯酸鹽氧化膜之特性分析與腐蝕行為”, 國立台灣科技大學機械系, P124-125, 2014.
[39] Felix Tjiang, Chen-Chia Chou, “Effect of processing parameters on soft regime behavior of plasma electrolytic oxidation of magnesium”, National Taiwan University of Science and Technology Department of Mechanical Engineering, pp. 94-95, 2016.
[40] Mingqi Tang, Weiping Li, Huicong Liu, Liqun Zhu, “Preparation Al2 O3 /ZrO2 composite coating in an alkaline phosphate electrolyte containing K2ZrF6 on aluminum alloy by microarc oxidation”, Applied Surface Science 258 (2012) 5869–5875.
[41] Keiji Watanabe, Masatoshi Sakairi , Hideaki Takahashi, Shinji Hirai ,Sadae Yamaguchi, “Formation of Al–Zr composite oxide films on aluminum by sol–gel coating and anodizing”, Journal of Electroanalytical Chemistry 473 (1999) 250–255.